1. Field of the Invention
The present invention relates to a solid imaging device having pixel lines in which photoelectric conversion sections such as photodiodes and so on is arranged linearly. Especially, the present invention relates to layout configuration of the solid imaging device.
2. Related Background Art
A CCD color linear image sensor is constituted by arranging photosensitive pixels in accordance with each color such as red, green and blue. Each of the photosensitive pixels is composed of a photoelectric conversion element such as a photodiode.
FIG. 10 is a diagram showing plain configuration of the conventional CCD color linear image sensor, FIG. 11 is an enlarged view near the end of a central pixel line 1b of FIG. 10, and FIG. 12 is an operational timing chart of the central pixel line of FIG. 10. The image sensor of FIG. 10 has image lines 1a, 1b and 1c in which a plurality of photosensitive pixels are linearly arranged. On upper surface of each of the pixel lines 1a, 1b and 1c, color filters (not shown) with red, green and blue colors are formed. During the time T1 in FIG. 13, the signal electric charge converted from the optical signal at each pixel line is transferred to the CCD registers 3a, 3b and 3c via shift electrodes 2a, 2b and 2c. And then along the direction of arrows, the signal electric charge transfers the inside of the CCD registers 3a, 3b and 3c in order. After arriving at the end of the CCD registers 3a, 3b and 3c, the signal electric charge is transferred to output circuits 4a, 4b and 4c. The output circuits 4a, 4b and 4c are provided corresponding to each of the image lines 1a, 1b and 1c. Each of the output circuits 4a, 4b and 4c outputs a color image signal OUT which is, for example, any of red, green and blue colors (RGB) signals.
As shown in FIG. 12, an image of a subject is picked up, while moving the image sensor 10 or the subject at a constant speed to the direction substantially perpendicular to the direction of the length of the pixel lines. More in detail, the color image signals are generated by conflating the result picking up the same position of the subject by means of three types of the image lines for RGB colors. Therefore, until all of the image lines picks up the same position of the subject, the data that each image line has picked up has to be stored into the memory. The further the adjacent pixel lines are spaced apart, the more the data amount being to store into the memory increases; accordingly, the memory with large capacity is necessary. Therefore, in order to reduce the cost and miniaturize the size of the image sensor, it is desirable to arrange each of the image lines as close as possible to each other.
Furthermore, if the pixel lines are spaced a long distance away from each other, distortion of resolution is prone to occur. Therefore, the optical configuration which allows the light of the subject to focus on the receiving surface of the photodiode constituting the pixel line and the mechanics which allows the image sensor to scan complicate.
Conversely, if the pixel lines are spaced only a short distance away from each other, the width of the CCD register should inevitably be narrowed. Therefore, the amount of the signal electric charge of the image sensor becomes small and the S/N ratio deteriorates.